1. Field of the Invention
The invention relates to a printing apparatus for transmitting and receiving data to/from an upper apparatus and, more particularly, to a printing apparatus for encrypting data which is transmitted and received to/from the upper apparatus and communicating.
2. Related Background Arts
Hitherto, as a data encryption system for encrypting data and transmitting and receiving the data between a terminal of an upper apparatus and a printing apparatus, a technique in which a client apparatus as an upper apparatus decides an encryption system which is used and makes encryption communication has been known (for example, refer to JP-A-10-210023 (refer to paragraph Nos. 0114 to 0160 and FIGS. 1 and 2)). According to such a technique, a network print system for executing encryption printing between the client apparatus and the printing apparatus is constructed, when the client apparatus selects whether or not print data is encrypted and transmitted and selects the mode for encrypting the data and transmitting it, the client apparatus selects a kind of encryption, encrypts the print data, and transmits it to the printing apparatus. The client apparatus has discriminating means which discriminates whether or not the encryption is necessary when the print data is transmitted on the basis of a connecting state between the client apparatus and the printing apparatus for executing the printing. The client apparatus transmits the encrypted print data to the printing apparatus on the basis of a discrimination result of the discriminating means. At this time, the discriminating means of the client apparatus discriminates whether or not the client apparatus and the printing apparatus have been connected through the Internet. If they are connected through the Internet, it is determined that the encryption is necessary.
If a communication protocol is a TCP/IP (Transmission Control Protocol/Internet protocol) and is also an Internet printing protocol, the discriminating means of the client apparatus determines that the printing apparatus has been connected through the Internet, and the data is encrypted. At this time, the discriminating means of the client apparatus discriminates whether or not the client apparatus and the printing apparatus exist in a same subnet. If it is determined that they exist in the same subnet, the data is not encrypted. The network print system can add or delete a kind of encryption which can be selected in the client apparatus. The kind of encryption can be changed in the client apparatus on a predetermined data unit basis. Further, by selecting a plurality of kinds of encryption, combining them, and designating order, the network print system can change the kinds of encryption in accordance with the combination order.
However, in the above conventional client apparatus or network print system, although the setting of the encryption and decryption can be made in detail from the client apparatus every communication, it is fairly difficult for the user having poor knowledge regarding the encryption kind to perform the selection of the encryption kind, the detailed setting of the encryption and decryption, and the like which are matched with the intensity of the encryption which the user wants to use. Although the above conventional client apparatus or network print system can also automatically set the encrypting and decrypting processes, in this case, there is such a discrimination reference that in the case where the client apparatus or the network print system has been connected through the Internet or in the case of the IPP (Internet Printing Protocol) printing for controlling the printer through the Internet, the encryption is performed, and if they exist in the same subnet, the encryption is not performed. However, in the conventional client apparatus or network print system, in the case where the user does not want to make the encryption even in the Internet connection or the IPP printing or he wants to make the encryption even if they exist in the same subnet, the automatic discrimination about the execution of the encryption cannot be arbitrarily made or the like, so that use efficiency is low.